The proposed study is a longitudinal follow up of 578 male non- smokers, initially evaluated in 1965 by respiratory symptom questionnaires and tests of forced expiration. After one additional year of data collection, the results of an 8-year prospective observation will be available to evaluate the probability of a detectible latent stage in obstructive pulmonary disease. The objectives are: 1) to document the natural history of obstructive pulmonary disease in a population of male non-smokers stratified by age, residential and social class histories; 2) to identify and characterize the population at greatest risk of developing obstructive pulmonary disease; 3) to determine the predictive value, if any, of testing for small airway dysfunction; and 4) to evaluate the sensitivity and specificity of analyzing spirometric curves in terms of exponential functions relating volume and time. The methods of study will include: 1) tracing subjects for complete ascertainment of the population which was tested in 1965; 2) interviewing subjects with NHLI respiratory questionnaire; 3) ascertaining peak flow and spirometry by NHLI criteria; and 4) describing the spirograms of both the current and 1965 studies in terms of exponential functions relating time, flow and volume.